Organophosphates are commonly used for the control of insects in agriculture and public health in developing countries like India. Many of them have become less effective due to the development of resistance by the target insects. To combat this problem, novel phosphorothioate derivatives of hydroxybenzaldehyde were synthesized and screened for their toxicity to the stored product insect Rhizopertha dominica and Tribolium casteneum in comparison with the standard methyl parathion. The results indicate that the O, O-dimethyl phosphorothioates were more toxic than the diethyl derivatives and the toxicity was comparable with methyl parathion.